1. Field of the Invention
The present invention relates to a display device, and more particularly, to a white organic light emitting device having high light emission efficiency.
2. Description of the Related Art
Organic light emitting devices (OLEDs) are self emissive display devices that use light generated by combining electrons and holes supplied to a fluorescence or phosphorescence organic compound thin film (hereinafter, an organic thin film). Generally, an OLED has a structure in which an anode, a hole transporting layer, a light emitting layer, an electron transporting layer, and a cathode are sequentially formed on a substrate.
A white OLED emits white light, and can be used as a paper-thin light source, a backlight for a liquid crystal display device, or a full color display device that employs a color filter. Approaches to manufacturing white OLEDs can be largely classified into two methods. The first method is making a light emitting layer as a single layer (hereinafter, the first method) and the second method is dividing the light emitting layer into multiple layers (hereinafter, the second method).
The first method includes a method of doping red, green, and blue dopants in one host, and a method of doping red and green dopants in a blue host. However, the light emitting layer formed using the first method has reduced light emission efficiency since energy transfer to the dopants is difficult.
In the second method, a light emitting layer can be configured by stacking a red light emitting layer, a green light emitting layer, and a blue light emitting layer. However, this produces a light emitting layer with low light emission efficiency due to a large current applied to the light emitting layer. Further, it is difficult to obtain three uniform primary colors due to excessive energy transfer within the light emitting layer.